Question

我的查询有问题：我有一张表，其中列出了客户下的订单

orders: customer_id, payment_method ...some other field

如果客户至少使用特定付款方式付款，我需要提取customer_id和'YES'

我试过这样的事情：

SELECT DISTINCT o.customer_id, 
CASE WHEN o.payment_method = 10 THEN 'YES' ELSE 'NO' END AS credit_card
FROM orders AS o
WHERE o.year = 2012
ORDER BY o.customer_id

但是如果客户使用不同的付款方式付款，则显示两条记录，一条带有“是”，一条带有“否”......可能只获得一个值？

Answer 1

SELECT   o.customer_id, 
         IF(MAX(IF(o.payment_method=10, 1, 0)) = 1, 'YES', 'NO') credit_card
FROM     orders o
WHERE    o.year = 2012
GROUP BY o.customer_id

Answer 2

您可以使用group by进行自联接，并在连接表中测试NULL（未经测试）：

SELECT customer_id, IF(p.customer_id IS NULL, 'NO', 'YES')
FROM orders o
LEFT OUTER JOIN orders p ON o.customer_id = p.customer_id AND p.payment_method = 10
    AND p.year = 2012
WHERE o.year = 2012
GROUP BY o.customer_id
ORDER BY o.customer_id

不确定问题是否需要p.year = 2012条件。

MYSQL查询条件语句

2 个答案: